The immunoglobulin can be prepared from either porcine or bovine blood collected for example at abattoirs from inspected animals. The preparation from porcine blood has application in the rearing of neonatal pigs while that from bovine blood has potential use in the rearing of calves. The following description is directed primarily to the porcine application.
The neonatal piglet is born without the ability to fight disease and is dependent upon colostral and later milk from the sow to provide immunoglobulins which confer passive immunity to disease for the first 2 to 3 weeks of life. The piglet's endogenous immune system begins to function and produce antibodies in response to environmental stimuli at approximately 2 weeks of age. On an average, 1.5-2.0 pigs per litter of 8-10 are lost between birth and weaning at 3-5 weeks of age as the result of a variety of sow and piglet related factors, including the inability of the piglet to obtain sufficient immunoglobulins from the sows' clostrum. Problems at lactation, extra large litters, within litter competition, poor nursing sows and sow death resulting in partial starvation and weakness leading to chilling and crushing which account for many of these losses. Clearly, a milk replacer imparting the required passive disease immunity would allow piglets to be raised from birth independent of the sow and thereby reduce piglet mortality that is most pronounced during the first 2-4 days of life (Van der Hyde, H. 1972, Proc. Br. Soc. Animal Prod. 33-36).
The availability of a milk based immunoglobulin enriched product which can be used in milk replacer formulation will allow for the rearing of neonatal pigs in a practical environment separate from the dam and allow for populating of new swine units by hysterectomy with pigs that are Specific Pathogen Free (SPF). Traditionally artificial rearing and derivation of SPF pigs was only possible under sterile conditions impractical at the farm level. This system of raising SPF pigs required specialized and expensive equipment. Artificial rearing iof neonatal pigs in a non-isolated or "commercial" environment has met with little success as the piglet is deprived of sow's colostrum and later milk required to provide the immunoglobulins which confer passive immunity to disease-causing and other organisms encountered in a non-isolated environment. A more practical approach would be to surgically remove the piglets from the sow by either caesarean section or hysterectomy and rear them from birth in a "commercial" (non-isolated) environment providing disease resistance from birth by supplementing the milk replacer with porcine immunoglobulins. The weaker pigs in a naturally farrowed litter could be selected soon after birth and reared artificially away from the sow. Those piglets contributing most to the early post-natal mortality could thereby be saved.
Scoot and Coworkers (J. of Animal Science, 1972, Vol. 35, Pages 1201-1205) obtained a survival rate of 75% or more when immunoglobulins were fed for 10 days postpartum to three lots of pigs and this did not differ significantly from control piglets nursing from their dam. Corresponding survival rates of the negative control pigs was 0.33 and 25%. Similar results were obtained by McCallum, Elliot and Owen in 1978 (Can. J. Animal Sci., Vol. 57, Pages 151-158).
The immunoglobulins required to confer passive disease immunity are also present in porcine blood, adequate quantities of which are available in meat packing plants. Currently such porcine blood is processed to produce blood meal. Isolation and concentration of these immunoglobulins from porcine blood has been previously accomplished by cumbersome methods in quantities sufficient to demonstrate that the immunoglobulins so derived can be added to the diet of neonatal pigs removed from the sow at birth and confer upon them the passive immunity to disease which will allow them to survive in a commercial environment, thereby ensuring the success of artificial rearing.
The mechanism by which immunoglobulins can be removed from porcine blood has been a subject of investigation for many years. Methodology employed to-date has been essentially a batch multi-step process which is slow, cumbersome, low yielding and not readily adaptable to commercial production.
Newson (Canadian Pat. No. 1,046,407, 1979) describes a batch process for the production of a product which contains only 20% immunoglobulin. This means that 75-90 g of the product must be fed to meet the suggested first day requirement of 15 g of immunoglobulin: this quantity of material alone already exceeds the daily dry matter requirement of a young pig (67.5 g) and leaves no room for the addition of skim milk powder (SMP) fat, minerals or vitamins. Casein, a normal constituent of SMP (25%), is essential for clot formation in the stomachs of young pigs.
A further method, belonging to the prior art (Eibl. M. Canadian Pat. No. 1,112,166, 1981), describes the preparation of a high purity immunoglobulin (80% pure); however, the method of preparation is extremely long and involved and would not be economically feasible.